The advantages of less invasive methods of abdominal surgery have been well documented. Reduced infection rates, decreased patient trauma and faster healing times have all been associated with the use of laparoscopic procedures, in which small surgical instruments are introduced into the abdominal cavity through the working channel of a trocar or other access device inserted through the abdominal wall muscle.
During these procedures, the abdominal cavity remains essentially a closed system. In order to improve visibility and increase working space for surgeons, it is preferable to distend the abdominal wall. This is usually accomplished through gas insufflation, in which carbon dioxide or another gas is introduced into the abdominal cavity to distend the abdominal wall and increase the volume of the abdominal cavity
Insufflation is typically accomplished using needle assemblies having a hollow cylindrical configuration. A needle having a sharpened distal tip is forced through the abdominal wall to provide access to the abdominal cavity through an insufflation channel. Once the sharpened tip is within the abdominal cavity, care must be taken to avoid puncturing internal organs. For this reason an obturator or stylet has been provided with the insufflation needle. As soon as the needle penetrates the abdominal wall, a blunt tip of the obturator moves beyond the sharpened tip of the needle to inhibit the further penetration of tissue.
During the insufflation process, it is desirable to maximize the flow of gases into the abdominal cavity to reduce the inflation time. Often, a patient will require as much as three liters of insufflation gas. With a typical insufflation flow rate of 600 milliliters per minute, this volume will require five minutes to fully insufflate the cavity. Even a slight reduction in the period of insufflation could significantly reduce operational procedure time and therefore result in a significant cost savings to the hospital and patient.
It is also important to ensure rapid protection of internal organs from the sharp needle tip following penetration of the abdominal wall. Typically, insufflation needle stylets or obturators are biased from a proximal position, wherein the sharpened tip is unprotected to facilitate penetration of the abdominal wall, to a distal position where the sharpened tip is isolated to prevent damage to the interior organs. A fast transition from the proximal position to the distal position increases the safety of the insufflation needle.
An insufflation needle assembly that promotes both rapid insufflation and fast transition of the obturator to isolate the sharp tip of the needle has been described in U.S. Pat. No. 6,656,160 to Taylor, Johnson and Hilal. In the '160 patent, an insufflation needle apparatus is disclosed in which the obturator is formed from a metal tube that is machined to remove portions of the obturator wall. Removing portions of the obturator wall reduces the mass of the obturator, resulting in a faster transition time and thus better protecting internal organs from inadvertent puncture wounds. Also, removing portions of the obturator wall increases the cross-sectional area of the insufflation channel, resulting in an increased insufflation rate.
The needle assembly of the '160 patent provides benefits in terms of safety and efficiency, but the costs associated with machining the metal obturator portion of the assembly also increases the cost of the assembly. Thus, a method of manufacturing the obturator that is more cost-efficient would result in significant savings to hospitals and patients, while maintaining the safety and efficiency of assemblies having reduced obturator wall portions.